Effects of Electrode-Tissue Proximity on Cardiac Lesion Formation Using Pulsed Field Ablation

Figures

• 

  Figure 1.. Offset tool and experimental setup. Pulsed field ablation (PFA) catheter with linear 4-electrode array with offset tool open and electrode 1 on the far left (A). The catheter located within the offset tool (with transparent front view) as well as a rendering of the cardiac pulsed field ablation lesion is shown (B). Experimental setup during epicardial PFA lesion creation. The chamber was filled with heparinized blood prior to initiating pulsed field ablation deliveries. C, During placement of the offset apparatus with electrode array positioned against epicardial surface, there was direct electrode-tissue proximity (0 mm, left) or the catheter was pulled back against the pins to ensure consistent distance from the tissue for 2 mm (middle) and 4 mm (right) electrode-tissue distances (D).

• 

  Figure 2.. Visual comparison of the 2 COMSOL Multiphysics geometries used in the numerical simulations at a distance of 2 mm from tissue. Both parts have the blood (and offset tool) cut out for better clarity through a plane passing through the center of the experimental catheter. A, Numerical model. B, Numerical model without offset tool. The blood pool and myocardium were extended by 10 mm on each side to prevent the edge of the model space from affecting the results.

• 

  Figure 3.. Sample lesion images. We need to change this Figure legend to as follows: Shown are superficial tetrazolium chloride (TTC) stained images from transversely cut tissue slices (left) at 0 mm, 2 mm, and 4 mm offset as well as uncut tissue slices (lesions seen from above, width measurements indicated by yellow lines, right).

• 

  Figure 4.. Lesion depth (A and B) and width (C and D) decreased significantly as the distance between epicardial surface and electrodes increased. Shown are individual lesion depths (in mm) with linear regression curves (A: linear slope −0.7413, R2=0.91; C: linear slope=−0.8979, R2=0.65) as well as Box-Whiskers plots with median, 25th to 75th percentile and minimum to maximum whiskers (B and D). Lesion depth-averaged 4.3±0.4 mm, 2.7±0.4 mm, and 1.3±0.4 mm for the 0-, 2-, and 4-mm electrode-tissue distances respectively. Lesion width averaged 9.4±1.1 mm, 7.5±0.8 mm, and 5.8±1.4 mm for the 0-, 2-, and 4-mm electrode-tissue distances respectively. One-way ANOVA analysis using the Tukey multiple comparison test showed significant differences between the 0 mm, 2 mm, and 4 mm groups (P<0.001 for depth, and P<0.01 for width).

• 

  Figure 5.. Numerically predicted lesion sizes. This figure shows the Numerical model (blue area, continuous outline) compared with the Numerical model without the offset tool (pink area, dotted outline). The offset tool induced some additional lesion formation at the edges, where the concentration of the current density resulted in higher local electric field in comparison to the unlimited model, which is most obvious in the top view and consistent with the experimental results shown in Figure 2.

• 

  Figure 6.. Lesion depth as a function of offset distance observed experimentally (ex vivo), compared to lesion depth calculated using a numerical model mimicking the experimental model (numerical model), as well as using a model in which the offset tool was removed (numerical model without offset tool).